Phase Change Random Access Memory (PCRAM) technology is developed based on the concept that a phase change film can be used as a phase change storage media. As a new type of non-volatile memory, PCRAM has the advantages similar to a flash memory, including fast read/write speed, more read/write cycles, long endurance, smaller unit area, and multi-value storage, etc., and it has become a most researched topic in the field of non-volatile memory.
In a PCRAM, the storage data is changed by performing a thermal treatment on the phase change layer which records the data. The phase change material of the phase change layer is able to switch between crystalline state and amorphous state according to the heating effect caused by an applied current. When the phase change layer is at the crystalline state, the resistance of the PCRAM is relatively low, the value assignment of the PCRAM is “1”. When the phase change layer is at the amorphous state, the resistance of the PCRAM is relatively high, the value assignment of the PCRAM is “0”. Therefore, the PCRAM is a non-volatile memory using the resistance difference of the phase change layer at the crystalline state and the amorphous state.
FIG. 1 illustrates an existing PCRAM. As shown in FIG. 1, the PCRAM includes a substrate 10. Metal interconnect structures are formed in the substrate 10. The PCRAM also includes a dielectric layer 20 formed on the substrate 10. Further, a bottom contact electrode 21 is formed in the dielectric layer 20. The bottom contact electrode 21 is connected with the metal interconnect structures in the substrate 10. Further, the PCRAM also includes a phase change layer 22 formed on the dielectric layer 20 and the bottom contact electrode 21.
When the bottom contact electrode 21 is connected with an electrical power source, the bottom contact electrode 21 is able to generate heat; and the phase change layer 22 is heated. Thus, the crystallinity of the phase change layer 21 is changed; and the logic value stored in the phase change layer 21 is changed.
However, the performance of the PCRAM needs further improvements. The disclosed device structures and methods are directed to at least partially solve such a problem and related problems.